Post-hoc analysis of clinicopathological factors affecting lateral lymph node metastasis based on STELLAR study for rectal cancer

Abstract

Purpose

In post-hoc analyses of phase III randomized controlled study (STELLAR), to analyze the prognostic impact of lateral pelvic lymph node (LPLN) metastasis in locally advanced rectal cancer (LARC).

Methods

LPLN metastasis was defined as a short diameter > 7 mm on magnetic resonance imaging (MRI). The study included 591 patients with LARC. All patients received neoadjuvant (chemo)radiotherapy combined with radical resection.

Results

Among 591 patients, 99 (16.8 %) were diagnosed with LPLN metastasis, mostly with unilateral metastasis (79.8 %), with internal iliac lymph node metastasis being more common (81.8 %). Significant differences were found among with and without LPLN metastasis in rectal segmentation (P=0.001), N disease (P<0.001), mesenteric LN metastasis or not (P=0.030). The median follow-up time was 34.0 months, three-year disease-free survival (DFS), overall survival (OS), and metastasis-free survival (MFS) were significantly lower in LPLN metastatic group than those in LPLN non-metastatic group (51.4 % vs. 68.2 %, P<0.001; 71.8 % vs. 84.2 %, P=0.006; 60.8 % vs. 80.1 %, P<0.001), respectively; while there were no significant differences in locoregional recurrence (11.4 % vs. 8.5 %, P=0.564). Multivariate analysis found that LPLN metastasis was an independent prognostic factor affecting DFS (P=0.005), OS (P=0.036), MFS (P=0.001). No significantly survival benefit was observed for the short-term radiotherapy based total neoadjuvant therapy compared to long-term concurrent chemoradiotherapy.

Conclusions

LPLN metastasis observed by MRI should be considered in LARC patients, especially in populations with low rectal cancer, N2 disease, and mesenteric LN metastasis. LPLN metastasis diagnosed by MRI is a significant and independent risk factor and is associated with worse DFS, OS, MFS.